In a relay backhaul link of a wireless communication system such as a long term evolution (Long Term Evolution, LTE) system or a long term evolution-advanced (Long Term Evolution Advanced, LTE-A) system, a device needs to be tested. During a test process, an SNR specified by the system is needed. In a signal test process, the SNR of a receiving end is set to a specified minimum index.
However, in a multi-output scenario, because a precoding technology is adopted in a signal sending device, the SNR measured by a signal receiving device (that is, the SNR of the receiving end) is an SNR containing a precoding gain, which does not satisfy the setting requirement, so that the test is invalid.